Many of the currently available controls for multi-speed power transmissions utilize a trimmer valve to control the rate of pressure rise in the on-coming friction device during a ratio interchange. These trimmer mechanisms or valves generally include an expandable chamber and a pressure regulating valve which regulates the on-coming clutch pressure relative to the pressure within the expanding chamber. Excess fluid supplied during the ratio interchange is vented to exhaust by the regulator valve of the trimmer valve. Thus, some oil is exhausted from the high pressure clutch filling circuit to the sump of the transmission. This oil flow represents a reduction in the overall efficiency of the transmission. A transmission control incorporating this type of trimmer valve is shown in U.S. Pat. No. 3,886,820, issued to Lentz on Jun. 3, 1975, and assigned to the assignee of the present invention.